Aceleracion De Hardware

What is hardware acceleration?
Normally your processor (CPU) does all the work when decoding video. When using hardware acceleration, most of that work is moved to the graphics processor (GPU). This significantly reduces the usage of CPU resources, which can be particularly useful if you have a relatively slow CPU. Graphics chips have dedicated circuitry for decoding video and thus can do itvery efficiently.
When should I use hardware acceleration?
Our recommendation is to use it only when really needed. That means use it only if you have a slow computer that gives very high CPU usage when playing videos.
Hardware acceleration only helps to reduce CPU usage. It does not give better video quality.
Usage of hardware acceleration increases the chance of playback problems. Usuallycaused by graphics driver bugs. So if you decide to use hardware acceleration, it is important to use up-to-date drivers.
What is the difference between CUVID, QuickSync, and DXVA?
DXVA is a generic interface for hardware acceleration that was created by Microsoft. It works with all brands of graphics cards.
CUVID is an interface created by NVIDIA and it only works with graphics cards from NVIDIA.QuickSync is an interface created by Intel and is supported only by the integrated GPUs of Intel Sandy Bridge and Ivy Bridge processors. A monitor needs to be connected to the GPU in order to use QuickSync functionality.
The advantage of CUVID and QuickSync is that the decoded video is copied back from GPU memory to CPU memory. This allows the video to be processed further after it has beendecoded. They basically act the same as a normal software decoder.
Most DXVA implementations keep the decoded video in GPU memory until it has been displayed. No additional processing can be done on the video. This is explained in more detail below.
DXVA "native" versus DXVA "copy-back"
DXVA implementations come in two variants: native and copy-back. Almost all implementations are of the nativetype. The LAV video decoder that is included in the pack offers both variants. The internal DXVA decoders in MPC-HC are native implementations, and ffdshow also offers a native implementation.
With the native type, the decoded video stays in GPU memory until it has been displayed. This brings some limitations with regard to playback. The DXVA decoder must be connected directly to the video renderer.There can be no processing filters in between. The video renderer must also support DXVA, which gives you a bit less freedom wth regard to the choice of renderers.
The reason for keeping the decoded video inside GPU memory is efficiency. Many (older) graphics chips haven't been optimized for copying data from GPU memory back to CPU memory. They can only copy data fast in the other direction.These chips are too slow to perform DXVA copy-back and will not give smooth playback when using it. This is the case for most older AMD/ATI and Intel chips.
DXVA implementations of the copy-back type will, as the name already suggests, copy the decoded video from GPU memory back to CPU memory. Such implementations don't have the limitations mentioned above and act similar to a normal softwaredecoder.
DXVA copy-back only works properly if the GPU can copy the data fast enough. Otherwise it will give stuttering video playback. GPUs that should be fast enough are:
NVIDIA: all models from the past few years
Intel: Intel HD Graphics 2000 and newer
AMD/ATI: Radeon HD 7xxx and newer
Copying the data results in a bit of CPU usage. This means that copy-back is a little less efficient thannative.
DXVA1 versus DXVA2
DXVA1 is used on Windows XP. DXVA2 is used on Vista and newer. Any other differences between the two versions are not important to know about.
The DXVA implementations in LAV Video decoder support DXVA2 only. The implementations in MPC-HC and ffdshow support both DXVA1 and DXVA2.
How to get subtitles with DXVA?
NVIDIA CUVID, Intel QuickSync, and DXVA copy-back all...